SN 2025aedz: A typical short-plateau type IIP supernova with rapid post-peak decline

Abstract

Type IIP supernovae (SNe IIP) are the most common subclass of core-collapse SNe in observations. However, SNe IIP with short plateaus of the order of tens of days are rarely observed. The progenitors for this kind of SN can help to address the red supergiant issue in stellar evolution. In this article, we report optical photometry and spectroscopy of SN\,2025aedz, a rapidly post-peak declining SN IIP with a typical short plateau. It exhibits a peak absolute magnitude of $M_r=-17.16\pm0.03$\,mag. The $r$-band light curve shows a steep early post-peak decline of $\sim5\,\mathrm{mag}\,(100\,\mathrm{d})^{-1}$ followed by a relatively short plateau, with a plateau duration of $\sim50\pm3$\,d. The overall spectral evolution is consistent with that of normal SNe~IIP, showing a blue continuum with prominent Balmer P-Cygni profiles during the photospheric phase, followed by the gradual strengthening of hydrogen and metal lines as the ejecta cools down, although the metal lines remain weak and the expansion velocities decline rapidly. SN\,2025aedz is similar to the short-plateau SN\,2018gj in its overall evolution, whereas its pronounced early decline resembles that of SN\,2023ufx, which has the shortest plateau duration known so far. The radioactive tail of the bolometric light curve implies a synthesized $^{56}$Ni mass of $\sim0.03\pm0.01\,M_\odot$. Motivated by the steep early decline, we performed radiation hydrodynamic simulations by exploring different circumstellar material configurations to reproduce its early bolometric light curve. These simulations indicate that SN\,2025aedz originated from a progenitor with a relatively low-mass hydrogen envelope, possibly produced through enhanced mass loss or binary interaction, while the steep early decline is likely explained by additional luminosity from circumstellar interaction.